Fix rpmdb: Thread died in Berkeley DB library

Solution
Please follow these steps to backup and rebuild the rpmdb database:

mkdir /var/lib/rpm/backup 
cp -a /var/lib/rpm/__db* /var/lib/rpm/backup/ 
rm -f /var/lib/rpm/__db.[0-9][0-9]* 
rpm --quiet -qa 
rpm --rebuilddb 
yum clean all

from:

https://cloudlinux.zendesk.com/hc/en-us/articles/115004075294-Fix-rpmdb-Thread-died-in-Berkeley-DB-library